7.7 Functions

PSPP functions provide mathematical abilities above and beyond
those possible using simple operators. Functions have a common
syntax: each is composed of a function name followed by a left
parenthesis, one or more arguments, and a right parenthesis.

Function names are not reserved. Their names are specially treated
only when followed by a left parenthesis, so that ‘EXP(10)’
refers to the constant value e raised to the 10th power, but
‘EXP’ by itself refers to the value of a variable called EXP.